Re: [RFC] clocksouce implementation for powerpc
From: Sergei Shtylyov <hidden>
Date: 2007-06-20 16:52:29
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Hello. Tony Breeds wrote:
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plain text document attachment (clocksource-add-settimeofday-hook.patch) From: Tony Breeds <tony@bakeyournoodle.com >
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I'm working on a clocksource implementation for all powerpc platforms. some of these platforms needs to do a little work as part of the settimeofday() syscall and I can't see a way to do that without adding this hook to clocksource.
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I'd like to see how this is used? If the code that uses this API change isn't ready yet, then this patch should really wait..
This is my current patch to rework arch/powerpc/kernel/time.c to create a clocksource. It's not ready for inclusion.
I guess it's been based on the prior work by John Stultz (and me too :-)?
powerpc needs to keep the vdso in sync whenener settimeodfay() is called. Adding the hook the to the clocksource structure was my way of allowing this to happen. There are other approaches, but this seemed to best allow for runtime. Initially I considered using update_vsyscall() but this is called from do_timer(), and I don't need this code run then :(
This has been booted on pSeries and iSeries (I'm using glibc 2.5, which uses the vdso gettimeoday())
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Index: working/arch/powerpc/kernel/time.c ===================================================================--- working.orig/arch/powerpc/kernel/time.c +++ working/arch/powerpc/kernel/time.c@@ -74,6 +74,30 @@ #endif #include <asm/smp.h> +/* powerpc clocksource/clockevent code */ + +/* TODO: + * o Code style + * * Variable names ... be consistent. + * + * TODO: Clocksource + * o Need a _USE_RTC() clocksource impelementation + * o xtime: Either time.c manages it, or clocksource does, not both
If you mean the init. part, this has been already done by me -- I've
implemented read_persistent_clock() and got rid of xtime setting. What's left
is to implemet update_persistent_clock() and get rid of timer_check_rtc()...
+ */
+
+#include <linux/clocksource.h>
+
+static struct clocksource clocksource_timebase = {
+ .name = "timebase",
+ .rating = 200,
Perhaps we even need to raise the rating to 300 or 400 -- according to
what <linux/clocksource.h> says?
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS, + .mask = CLOCKSOURCE_MASK(64), + .shift = 22,
PPC64 has issues with the fixed shift value, see:
http://patchwork.ozlabs.org/linuxppc/patch?id=11125
+ .mult = 0, /* To be filled in */ + .read = NULL, /* To be filled in */ + .settimeofday = NULL, /* To be filled in */
I don't quite understand why not just init them right away? The values
are fixed anyways.
+}; + /* keep track of when we need to update the rtc */ time_t last_rtc_update; #ifdef CONFIG_PPC_ISERIES
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@@ -666,8 +631,8 @@ void timer_interrupt(struct pt_regs * re if (per_cpu(last_jiffy, cpu) >= tb_next_jiffy) { tb_last_jiffy = tb_next_jiffy; do_timer(1); - timer_recalc_offset(tb_last_jiffy); - timer_check_rtc(); + /* timer_recalc_offset() && timer_check_rtc() + * are now called from update_vsyscall() */
I.e. in the softirq context...
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WBR, Sergei